Diagnosis and Conservation of Stone
Code
7417
Academic unit
Faculdade de Ciências e Tecnologia
Department
Departamento de Conservação e Restauro
Credits
6.0
Teacher in charge
Maria Amélia Alves Rangel Dionísio
Weekly hours
5
Total hours
70
Teaching language
Português
Objectives
At the end of this course the student will have acquired knowledge, skills and competences to:
- to identify the problems that affect the exposed stone materials, to characterise and interpret them and to propose solutions for the identified problems,
- to enable the student to acquire knowledge: i) on the genesis, properties and specificities of the materials under study, ii) on the degradation phenomena and on the driving mechanisms, iii) on the interpretation of the onsite behaviour of each specific material, on their decay products and the methods of diagnosis.
- to approach the methods of conservation and restoration, enabling the student to acquire knowledge on the basic procedures of the profession through the study of treatment methods and products as well as the methods used in their study, in the lab and onsite,
- the information is illustrated with results taken from research studies and from real case-studies.
Prerequisites
Good knowledge previously acquired in the course "Principles of Geology and Mineralogy"
Subject matter
Brief presentation of the curricular unity
Students presentation.
Aims of the curricular unity. Evaluation system.
Natural rock weathering: meteoric weathering or deuteric weathering.
Weathering and weatheribility.
Intrinsic weathering (the case of granites). Weatjhering as a chemical process of reaching equlibrium.
Weathering mechanisms: chemical and physical.
Silicates weathering. Hydrolisis. Goldisch series. Weathring due to cooling and exposition to weather agents. Contrast between feldspars and quartz behaviour. Thermal expansion. Clay minerals expansion.
Intrinsic versus extyrinsic factors.
Materials identification: macroscopic inspection, optical microscopy and SEM, chemical and physical-chemical methods, XRD, TGA, ATD, etc.
Sampling
Representative samples. Dimension of samples. Stone sampling in outcrops and monuments.
Laboratory Methods
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Enironmental Characterization
Temperature, relative humidity, rain and air composition. Climate and microclimate.
Identification of decay products
Visual inspection and optical fiber microscopes. Non-destructive tests. Ultrasounds; termography. Encoscopy. Georadar. Microdrilling.
Definition of a test program
Adaptation to each case and to each stone material
Stone conservation: main types of intervention
Cleaning, consolidation, protection
Brief presentation of each category. Reasons for its accomplishment.
Black crosts and biological colonization: decay or aestetic factors?
Powdreing and arenizatrion: strenght and strctural stability degradation.
Very porous stones applied outdoors and their protection.
Methods evaluation criteria
Eficiency, harmfullness and durability. Reversibility or retreatability.
Preliminary operations
Causes identification. Aims definition. Theoritical framing of conservation operations.
Real situation of pratical conservation
Safe solutions or of badly lesser? Importance of previous experiences. Limitation of conservation operations. Importance of maintenace operations.
Cleaning of stone surfaces
Distinction between crust and superficial deposit
Different process phases (daignostic, negotiation, execution).
Substrate Properties (petrographic type, decay state, hardness and mechanical strenght).
Dirtiness characteristics (type, coehsion, thickness).
Current Cleaning Methods
Soft versus agressive methods. Requisites that must be respected
Non-removable of original materials and patina conservation as a security measure of non agressiveness. Abscence of collateral damage.
Water Cleaning
Forms of use: drained, pressurized, vapor. Risks of infiltrations and mobilization of soluble salts.
Cleaning with abrasive methods
Sand blasting (dry or wet)
Claening with laser radiation
Brief presentation of the cleaning mechanism by fotonic abalation. Types of lase. The importance of beam transport way.
Conservation treatments
Description of some used methods of assay in these studies.
Consolidants
Efficiency: depth of penetration and mechanical strenght. Methods of laboratory for its determination.
Harmfullness: contrast of resistance and formation of interfaces; permeability to the vapor; chromatic variations.
Durability: assays of accelerated aging and in natural exposition;
Biocide Treatments
Evaluation of efficiency. Study cases. Recolonization monitoring
Documentation of conservation interventations
Cartographic essays
Mapping of decay conservation
Lexic of decay forms
Documentation of operations performed
Documentation of products and apllication methods
Documentation of final result of intervention
Pratical examples of conservation intervention case studies in limestones
-Aims, Study methods, some results
· Santa Cruz Church, in Coimbra.
· - Belém Tower
· Jerónimos Monastery Cloister
· Évora Cathedral
· Porta Especiosa, Coimbra
Teaching method
Exposition based on examples from investigation or pratical case studies of conservation and restoration.
Observation of samples from materials and visit to real case studies where materials and decay problems are presented and where forms of identification of decay are explained.
Caracterisation of materials properties based on laboratorial instrumentations, namely of:
- samples of stone deterioration forms
- stone samples in sound, or weathered, or treated state
Visit to workmanships whre great stone intervations were done and where it is possible to illustrate conservation techniques and to explain why they were choosed.
Evaluation method
1. Final exam, or three parcial tests, covering the full programme of the discipline (60% final note)
2. Report of laboratorial work + report of field work about the diagnosis of a study case (30% final note)
3. Study of articles + questionnaires or descriptions about study trips + exercises made in the practical lessons (10% final note)